For example, in a semiconductor device manufacturing process, a plasma processing such as an etching, a sputtering, a chemical vapor deposition (CVD) or the like is performed on a semiconductor wafer as a substrate to be processed.
As for a plasma processing apparatus for performing such plasma processing, there are used many different kinds of processing apparatuses and a capacitively coupled parallel flat type plasma apparatus is a typical one most commonly used among them.
In the capacitively coupled parallel flat type plasma processing apparatus, a pair of parallel flat electrodes (an upper and a lower electrode) is provided in a chamber, and a processing gas is introduced into the chamber. Further, a radio frequency electric field is formed between the electrodes by applying a radio frequency power to one of the electrodes to thereby form a plasma from the processing gas, which, in turn, can be used in performing a plasma processing on a semiconductor wafer.
To be specific, there has been a well known plasma processing apparatus for forming plasma by applying to an upper electrode a radio frequency power for generating plasma and then converting the plasma into an appropriate plasma state by applying to a lower electrode a radio frequency power for attracting ions. By employing such plasma processing apparatus for an etching process, a high reproducible etching process can be performed with a high selectivity (see, e.g., U.S. Pat. No. 6,423,242 B1).
In such a plasma processing apparatus, there is given rise on the side of a plasma source to a minor difference in the impedance between apparatuses or cleaning cycles due to dimensional tolerances or attachment errors of parts. However, the conventional plasma processing apparatus is not provided with a mechanism for solving the mechanical difference in impedance, so that process characteristics become different from one apparatus to another or from one cleaning cycle to another.